Beta blockers Flashcards
where are Beta 1 receptors located and what happens when they are stimulated/agonized?
Heart (AV node, SA node, atrial & ventricular muscles)…increase Heart rate & Contractility
CNS
Kidney (Juxtaglomerular cells)……increase Renin > stimulates RAAS
Adipose tissue (to a lesser extent)……increase Lipolysis
where are beta 2 receptors located and what happens when they are stimulated/agonized?
Smooth muscles, so it relaxes smooth muscles of the :
Bronchioioles……Bronchdilation
Blood vessels……Vasodialation
Uterus…stops uterine contraindications
GI tract………decrease motility
Bladder……increase urination
Pancreas (alpha cells)………increase glucogon > increase glucose > increase insulin
Liver……increase glucose > increase insulin
CNS
Eyes (ciliary body)……increase aqueous humor > increase intra ocular pressure
{pupils controlled by alpha 1 receptors}
Skeletal muscles……increase contraction
Heart (to a lesser extent)
Where are Beta 3 receptors located?
Adipose tissue
Bladder
Heart & smooth muscle (to a lesser extent)
Stimulating/Agonizing beta 1 receptors causes?
Vasoconstriction
Increase Heart rate & contractility
Increase Renin
Increase Lipolysis
Increase Glucogon?
Stimulating/Agaonizing Beta 2 receptors causes?
Vasodialation
Bronchodilation
Increase Insulin
What do Beta blockers/ Beta antagonist therefore do?
The opposite of beta agonist
what are the indications of Beta blockers?
1) Acute coronary syndrome & IHD
2) Chronic heart failure
3) Atrial fribillation: to reduce ventricular rate & maintain sinus rhythm (in paroxysmal A Fib)
4) Supraventricular Tachycardia (SVT): to restore sinus rhythm
5) Resistant HTN: as a 4th line treatment
6) Migraine prophylaxis
7) Thyrotoxicosis
8) Glaucoma
9) Tremors/Anxiety
What are the side effects of Beta blockers?
Bradycardia
Bronchospasm/Bronchoconstriction (due to non-selective beta blockers)
Heart block
Hypotension >:
Cold extremities
Erectile dysfunction
(due to non-selective beta blockers- peripheral vasoconstriction effect)
Headache
Diarrhea
Fatigue
Insomnia
Nightmares
Hypoglycemia unawareness by blocking the sympathetic nervous system (so symptoms like tachycardia, tremors,diaphoresis, confusion are masked)
Symptoms of Beta blocker overdose:
Hypotension
Bradycardia
Heart block
Mental status change: Lethargic
Antidote:
Fluids
Atropine (Ach receptor blocker/antagonist. Ach decreases HR, BP & ect. so blocking this increases HR, BP and thus overides the beta blocker blockade )
Glucogon (same as Atropine)
What drugs should NOT be used with Beta blockers?
Non-Dhydropyridine Calcium Channel blockers:
Verapamil
Diltiazem
because together they cause:
Heart failure
Bradycardia
Asystole (flat line)
Which Beta blockers are preferred for heart failure
Bisoprolol, Carvedilol & Metoprolol
What type of beta blockers are preferred in HTN emergencies and renal patients?
Mixed Beta blockers (Labetalol & Carvedilol) because they block beta 1, beta 2 & Alpha 1 receptors. However the best drug to use in HTN emergencies is Sodium Nitroproside.
Mixed beta blockers have minimal effects on GFR, thus safe to use in renal patients.
Note: Labetalol can be used in place of Metyldopa when treating HTN in pregnancy
All beta blockers are contraindicated in?
Hypotension
Heart blocks
Sink sinus syndrome
Cardiogenic shock
Caution in:
1) Diabetic patients, because their side effects can mask the signs of Hypoglycemia, such as tachycardia. And propranolol, metoprolol, and atenolol can result in consistently elevated fasting blood glucose levels (Hyperglycemia). DM friendly Beta blockers are: Carvedilol & Nebivolol
2) Hepatic failure, because it requires dosage reduction
3) Heart failure, because it requires a low starting dose, then a gradual increase to target dose.
Selective/Cardioselective beta blockers block only ?
Beta 1 receptors
What type of beta blockers are safe to be used in Asthma & COPD?
Selective/Cardio selective beta blockers
Non-selective beta blockers block which receptors?
Beta 1& Beta 2
